1. Field of the Invention
The present invention relates to a recording medium cartridge in which a recording medium is housed within a cartridge case, and more particularly to the material of the cartridge case.
2. Description of the Related Art
As examples of recording medium cartridges, in which a commercially-available recording medium such as a magnetic recording medium and an optical recording medium is housed within a cartridge case, there are a magnetic disk cartridge housing a magnetic disk (such as a flexible disk, a magneto-optical disk, etc.), a magnetic tape cartridge housing magnetic tape (such as VTR tape, tape for external storage units for computers, etc.), and an optical disk cartridge housing an optical disk. The cartridge cases for these recording medium cartridges are normally formed by molding resin.
These recording medium cartridges are conveyed to a recording/reproducing unit by manual operation, and recording or reproducing is performed. In addition, a large number of recording medium cartridges are achieved in a library, and under computer control, a predetermined recording medium cartridge is automatically taken out. The recording medium cartridge is conveyed to a recording/reproducing unit, in which recording or reproducing is performed. After use, the recording medium cartridge is automatically conveyed and archived in the library. In such an automatic system, it is necessary to detect a recording medium cartridge. It is possible to use a mechanical sensor to detect a recording medium cartridge. However, it is preferable that a recording medium cartridge be detected with non-contact by an optical sensor such as an infrared sensor, etc.
In addition, in recording medium cartridges, recording mediums with recording capacity enhanced by an improvement in recording density are housed in cartridge cases of the same shape. They are used, while interchangeability is being assured. To discriminate between the previous and new cartridges, the color of the cartridge case is often changed.
In the case where a cartridge case is molded with resin, there is a need to take shock strength, and moldability into consideration. In addition, to reliably perform non-contact detection by the aforementioned infrared sensor, it is necessary that an infrared transmissivity for a cartridge case be, for example, 5% or less.
However, in the case where the color of a cartridge case is changed as mentioned previously, the aforementioned shock strength, and moldability will be conflicting elements, if the cartridge case is colored in a bright color such as blue, yellow, etc. Thus, there are cases where it becomes difficult to satisfy both requirements.
The present invention has been made in view of the circumstances mentioned above. Accordingly, it is the primary object of the present invention to provide a recording medium cartridge that is capable of having appropriate infrared transmissivity, while assuring stock strength, frame resistance, and moldability, when changing the color of a resin cartridge case housing a recording medium.
To achieve this end, there is provided a recording medium cartridge comprising a resin cartridge case housing a recording medium. The resin cartridge case contains titanium dioxide by 0.1 to 1.2 wt %.
The resin cartridge case may be composed of polycarbonate resin, fiber-reinforced polycarbonate resin, an alloy resin of polycarbonate and acrylonitrile butadiene styrene copolymer (ABS), ABS resin, polystyrene resin, etc. Particularly, polycarbonate resin is preferred.
The amount of titanium dioxide added is 0.1 to 1.2 wt %, preferably 0.1 to 1.0 wt %, and further preferably 0.15 to 0.8 wt %.
According to the present invention, the resin of the resin cartridge case contains titanium dioxide by 0.1 to 1.2 wt %. As a result, the color of the cartridge case can be changed to a bright color such as blue, yellow, etc., while assuring shock strength, moldability, and infrared transmissivity.
To reduce infrared transmissivity to about 5% or less and obtain stable detection by an infrared sensor, it is necessary that the addition of titanium dioxide be 0.1 wt % or greater, preferably 0.15 wt %.
On the other hand, the cartridge case of the recording medium cartridge is normally required to have a shock strength which can resist shock due to a fall from a height of 0.7 to 1 m. To assure moldability in addition to the stock strength, it is necessary that the amount of titanium dioxide added be 1.2 wt % or less, preferably 1.0 wt % or less, and further preferably 0.8 wt % or less. That is, titanium dioxide plays a catalytic role and has the property of accelerating the thermal degradation of resin, for example, polycarbonate resin. Because of this, titanium dioxide reduces the molecular weight of resin and therefore reduces shock strength. In the step of molding the cartridge case, the stay of resin within a molding machine for about ten minutes cannot be avoided when the machine is started, and consequently, the thermal degradation of resin progresses. To avoid this phenomenon and assure shock strength, and to assure infrared transmissivity, it is preferable that the added amount of titanium dioxide be in the aforementioned range.